In production processes of semiconductor devices, pressure sensitive adhesive sheets have conventionally been used, and on a pressure sensitive adhesive layer of such a pressure sensitive adhesive sheet, a release liner having a release layer made from a release agent containing a silicone compound is generally laminated on a substrate for protecting the pressure sensitive adhesive layer.
However, silicone compounds generally have a property such that they easily migrate. Therefore, in semiconductor fields, when such a pressure sensitive adhesive sheet is used, it is considered that a silicone compound constituting a release layer migrates to a pressure sensitive adhesive layer to cause a defect on circuits of semiconductor devices and the like. Accordingly, a release liner having a release layer made from a release agent not containing a silicone compound has been desired.
For the release agent not containing such a silicone compound, there are proposed an alkyd resin release agent, an olefin resin release agent and a long chain alkyl group-having acryl resin release agent (hereinafter sometimes referred to long chain alkyl release agent).
However, the alkyd resin release agent has a problem such that the use thereof is limited on adhesives because of having high peel strength, the olefin resin release agent has a problem such that a pressure sensitive adhesive layer cannot be formed on a release liner because of having inferior heat resistance, and the long chain alkyl release agent has a problem such that a pressure sensitive adhesive agent cannot be applied on a release liner because of having inferior solvent resistance and further has inferior adhesion to a substrate such as films or the like.
Under the circumstances, a release agent composition prepared by introducing an ultraviolet ray curable functional group in a long chain alkyl resin is proposed in order to solve the above problems in the long chain alkyl release agent (for example, referred to JP-A-2003-183619).
Furthermore, proposed are release agent compositions prepared by introducing a crosslinking functional group such as a hydroxyl group, carboxyl group or epoxy group into a long chain alkyl resin (for example, referred to JP-A-2003-147327 and JP-A-2000-290610). However, when such a crosslinking structure is formed by introducing a functional group into a long chain alkyl resin which is a major agent, the freedom of the long chain alkyl group is decreased so that the surface energy of a release layer is hard to be lowered and thereby it is difficult to control peel strength thereof.
It is an object of the invention to provide a release agent composition not having a bad influence upon electronic parts and the like and having excellent solvent resistance, heat resistance, release properties and adhesion to substrate, and it is another object of the invention to provide a release liner having a release layer made from the release agent composition.